The principle of freedom in establishing an infringement of Article 101 TFEU allow the Commission, on whom the burden of proof rests, to choose the method of evaluation of evidence that it considers most appropriate.

The competition authorities favor documentary evidence. Thus, according to settled case law, the proof of the absence of another plausible explanation is not necessary for the finding of a restrictive agreement where it stems, not from the parallel behavior of the parties but from documentary evidence establishing a concurrence of wills. No principle of EU law precludes the Commission from relying on a single piece of evidence to find the existence of an infringement of Article 101(1) TFEU, provided that its evidential value is undoubted and that the document by itself definitely attests to the existence of the infringement in question. Evidence can be in the form of documents, telexes, faxes, internal memos, the minutes of meetings, or handwritten or electronic correspondence between undertakings. Nevertheless, the presumption of innocence precludes the national court from inferring from the mere dispatch of an electronic message – used for the concerted practice –  that it constitutes sufficient evidence to establish that the addressees of that message were aware of its content.

According to the general rules regarding evidence, the reliability and, thus, the probative value of a document depends on its origin, the circumstances in which it was drawn up, the person to whom it is addressed and its content. Particularly high probative value may be attached to statements which are made by a direct witness of the circumstances to which they relate and which are contemporaneous with those facts. Thus, notes taken during an anticompetitive meeting by one of the participants will have a very high probative value and will not need to be corroborated by other evidence even if they are provided by a leniency applicant, whereas minutes drafted shortly after a meeting by a person who was not present, based on information obtained from a participant will be of lower probative value. E-mails exchanged between the participants of a meeting which reproduce the notes taken on that occasion have a very high probative value. The probative value of a document is not called into question by the fact that its origin is unknown, that it was not discovered on the premises of the claimant but on those of the other accused undertakings, that the evidence has already been used in another case or that it was provided to the Commission further to a request for information from the latter and not spontaneously. Similarly, contradictory statements made after the Statement of Objections in support of a leniency application or during the administrative procedure do not call into question the credibility of data consisting of records of meetings drafted by participants – contemporaneous with the infringement – and which is corroborated by the statements of other leniency applicants. Although a handwritten note where the undertaking is not identified and which does not refer to a particular meeting, cannot by itself establish the concerted action, the fact that an undertaking is not mentioned in a document does not prevent its participation in an agreement from being proven when this has been established in other documents. Conversely, the mere reference to an undertaking in notes taken by a third party during an anticompetitive meeting is not enough for that undertaking to be regarded as a participant in the infringement. In addition, in order to establish the participation of an undertaking in concerted behavior, the Commission can take account of documents submitted by that undertaking as part of its application for leniency, although paragraph 6 of point 26 of the Leniency Notice in principle protects such evidence, where the evidence at issue did not allow it to establish additional facts increasing the gravity or the duration of the infringement.

Where there is no documentary evidence, which is frequently the case for secret cartels, the existence of an agreement can be established through the existence of a firm, precise and consistent body of evidence regardless of the value of each piece of evidence when taken in isolation.

Evidence can also be in the form of telephone calls, witness testimony or statements made by undertakings themselves. In the latter case, there is a particularly high probative value afforded to those which cumulatively: i) are reliable, ii) are made on behalf of an undertaking, iii) are made by a person under a professional obligation to act in the interests of that undertaking, iv) go against the interests of the person making the statement, v) are made by a direct witness of the circumstances to which they relate and, iv) were provided in writing deliberately and after mature reflection. If, according to the court, some caution as to the evidence provided voluntarily by the main participants in an unlawful agreement is generally called for in view of the possibility that they might tend to play down the importance of their contribution to the infringement and maximize that of others, seeking to benefit from the application of the Leniency Notice in order to obtain a reduction in the fine does not necessarily create an incentive to submit distorted evidence. Indeed, any attempt to mislead the Commission could call into question the sincerity and the completeness of cooperation of the person seeking to benefit from it, and thereby affect the outcome of the application. The fact that the Commission subsequently considers that a leniency applicant does not deserve to obtain the maximum reduction of the fine does not mean that it regards the evidence provided to be unreliable, but only that, in view of the other material that it has, the evidence did not provide it with significant added value. Similarly, the fact that the undertaking handed over documents at a very advanced stage of the administrative procedure does not constitute evidence or proof that those documents are not authentic, but on the contrary shows that it cooperated with the Commission throughout the procedure. The credibility of statements made and evidence provided by an undertaking in the context of a leniency application is not further called into question on the grounds that they were provided after the failure of settlement proceedings. If such evidence is contested by several undertakings, account may nevertheless be taken of such evidence provided that it is corroborated by other elements. Corroboration may be provided, inter alia, through the statements of other undertakings made in the context of their own leniency application. The General Court cannot require that evidence used only to corroborate other elements have the same value as evidence that would be sufficient in itself.